JFS:
Food Chemistry and Toxicology
Volatiles and Oxidative Changes in Irradiated
Pork Sausage with Different Fatty Acid
Composition and Tocopherol Content
C. JO AND D.U. AHN
FoodChemistryandToxicology
ABSTRACT: Aerobic-packaged sausage irradiated at 4.5 kGy had higher (P < 0.05) 2-thiobarbituric acid reactive
substances (TBARS) than those irradiated at 0 or 2.5 kGy at 0-d storage. Generally, TBARS of aerobic- or vacuumpackaged sausage prepared with lard were higher (P < 0.05) than those of sausage prepared with flaxseed oil or corn
oil. The amount of 1-heptene and 1-nonene increased (P < 0.05) with increased irradiation doses. Aldehydes,
ketones, and alcohols were not influenced by irradiation at 0-d storage. However, irradiation accelerated lipid
oxidation and increased the amount of aldehydes, ketones, and alcohols in aerobic-packaged sausage during
storage. The tocopherol content in the sausage influenced (P < 0.05) production of volatiles at different levels of
unsaturated fatty acids.
Key Words: fatty acid, irradiation, lipid oxidation, volatiles, pork sausage
Introduction
T
HE F OOD AND D RUG A DMINISTRATION
(FDA) approved irradiation for poultry
and red meat to control foodborne pathogens and extend product shelf life (Gants
1998). However, one of the major concerns
in irradiating meat is its effect on meat
quality. When molecules absorb ionizing
energy they become reactive and form
ions or free radicals that react to form stable radiolytic products (Woods and Pikaev
1994). These reactive substances oxidize
myoglobin and fat which may cause discoloration, rancidity, and off-odor in meat
(Murano 1995). Hashim and others (1995)
reported that irradiated (between 1.66
and 2.66 kGy absorbed doses) uncooked
chicken breast and thigh meat produced a
characteristic bloody and sweet aroma
that remained after the meat was cooked.
Patterson and Stevenson (1994) reported
that dimethylsulfide was the most potent
off-odor compound, followed by cis-3- and
trans-6-nonenal, oct-1-en-3-one, and methylthiomethane in irradiated raw chicken. Lipid oxidation by-products are considered important volatiles related to the
off-odor production in irradiated meat.
However, lipid oxidation in pre-rigor beef
irradiated at 2.0 kGy and stored at 2 EC in
modified atmosphere packaging (25% CO2
and 75% N2 ) did not increase (Lee and
others 1996).
The degree of unsaturation of a fatty
acid affects oxidation rate significantly.
The relative reaction rate of linolenic acid
(C18:3) with oxygen is much faster than
that of linoleic acid (C18:2) and oleic acid
(C18:1) (Frankel 1991). Although a minor
portion of total fatty acid, the content of linolenic acid has an impact on oxidative
stability and flavor of soybean oils (Miller
and White 1988, Liu and White 1992). Hau
and others (1992) reported that irradiation
of frozen grass prawns at 10 kGy reduced
levels of polyunsaturated fatty acids by
25% to 32%, possibly due to oxidation and
decomposition of lipids into volatile compounds. The amount of free fatty acids
was increased by irradiation at 10 and 15
kGy doses, and gamma irradiation at 15
kGy resulted in loss of phospholipids in
rice bran during storage (Shin and Godber
1996).
The oxidation of lipids in raw meat is
closely related to the antioxidant potential
of muscle tissues. Tocopherol is the major
antioxidant located in cell membranes
and protects membrane fatty acids and
cholesterol from peroxidative damages
caused by highly reactive free radicals
such as hydroxyl, peroxyl and superoxide
radicals (Buckley and others 1995, Liu and
others 1995). The dietary supplementation of vitamin E or direct addition of vitamin E to meat during processing determines tocopherol content in meat products. The increased vitamin E concentration in meat products can improve the
storage stability of raw meat during storage (Ajuyah and others 1993, Winne and
Dirinck 1996). The free radicals generated
by irradiation can destroy antioxidants in
muscle, reduce storage stability, and increase off-flavor production in meat
(Thayer and others 1993; Lakritz and others 1995).
Irradiation increased 2-thiobarbituric
270 JOURNAL OF FOOD SCIENCE—Vol. 65, No. 2, 2000
acid (TBA) values and carbonyl content in
ground chicken meat (Kanatt and others
1998). Lipid oxidation and the production
of volatile compounds were correlated
well, and hexanal and total volatiles represented the lipid oxidation status better
than any other individual volatile component in irradiated pork patties (Ahn and
others 1998a). However, little is known
about the effect of the irradiation on production of volatiles and lipid oxidation in
irradiated meat with different fatty acid
composition and tocopherol content.
The objective of this study was to determine the effects of irradiation on lipid
oxidation and production of volatile compounds in pork sausage with different fatty acid composition and tocopherol content.
Results and Discussion
Lipid oxidation
The fat contents of sausage with lard,
corn oil, and flaxseed oil were 10.3%,
10.5%, and 10.5%, respectively, and there
was no difference in fat content among oil
treatments. The sausage made with lard
had the highest content of oleic acid
(47.3%), and that made with corn oil and
flaxseed oil had high linoleic acid (42.3%)
and linolenic acid (38.2%), respectively.
The amount of a-tocopherol in sausage
was the highest with flaxseed oil and the
lowest with lard, but the difference was
small. However, the amount of g-tocopherol in sausage prepared with flaxseed
oil was 100- to 200-fold higher than that
prepared with lard or corn oil (Table 1).
© 2000 Institute of Food Technologists
Volatile compounds
Volatiles of vacuum-packaged pork
sausages at Day 0 (Table 4) indicated that
sausages prepared with lard produced
more 1-heptene and 1-nonene but less 1pentanol and 1-heptanol when irradiated
than when nonirradiated. Sausages made
with corn oil produced more 1-heptene, 1nonene, pentanal, 2-pentanone, and total
volatiles when irradiated than nonirradiated. Irradiated sausages made with flaxseed oil produced more 1-heptene, propanal, 1-nonene 2-pentanone, and total volatiles, but less 3-heptanol and nonanal
than when nonirradiated. More 1pentene+hexane was produced from sausages with lard than those prepared with
corn oil or flaxseed oil, resulting in higher
total volatiles for lard than for corn or flaxseed oil (p < 0.05). 1-Pentene and hexane
Table 1—Major fatty acids and tocopherol content of cooked pork sausages prepared with
different fat sources
Fatty acid composition
Fat source
Lard
Corn oil
Flaxseed oil
SEM
16:0
16:1
23.32a
13.46b
12.51b
1.57
18:0
18:1
(% of total fat)
22.01a
47.31a
8.05b
35.87b
7.16b
18.93 c
2.52
1.45
0.44
0.25
1.09
0.31
18:2
Tocopherol
18:3
a-tocopherol
g-tocopherol
(␮g/g sausage)
0.79c
0.12b
1.44b
0.24b
1.75a
24.17a
0.44
0.40
6.71c
0.00b
42.27a 0.00b
21.14b 38.21a
3.17
0.23
a-cDifferent letters within a column are significantly different (P < 0.05).
SEM: Standard errors of the mean.
Table 2—TBARS values (mg malondialdehyde/
kg) of irradiated cooked pork sausages prepared with different fat sources after 0-d storage
Irradiation
dose
Lard
Corn Flaxseed SEM1
oil
oil
Table 3—TBARS values (mg malondialdehyde/
kg) of irradiated cooked pork sausages prepared with different fat source after 8-d storage
Irradiation
dose
(mg malondialdehyde/
kg sausage)
Aerobic packaging
0 kGy
2.5 kGy
4.5 kGy
SEM2
Vacuum-packaging
0 kGy
2.5 kGy
4.5 kGy
SEM2
Lard
Corn Flaxseed SEM1
oil
oil
(mg malondialdehyde/
kg sausage)
1.45ay
1.69 ay
2.25 ax
0.09
1.20by
1.13by
1.72bx
0.04
1.08by
1.03by
1.53bx
0.06
1.06a
1.14a
1.13a
0.07
0.87b
0.77b
0.87b
0.05
0.79by 0.04
0.90 aby 0.08
1.18ax 0.07
0.07
0.05
0.04
0.10
Aerobic packaging
0 kGy
2.5 kGy
4.5 kGy
SEM2
Vacuum-packaging
0 kGy
2.5 kGy
4.5 kGy
SEM2
5.71a
5.20a
5.01a
0.25
4.50b
3.50b
3.88b
0.29
4.70b
3.84b
4.53ab
0.31
0.21
0.32
0.27
1.27a
1.11a
1.14a
0.04
1.07b
0.90b
1.00b
0.05
0.92c
0.97b
0.99b
0.04
0.05
0.03
0.04
a,bDifferent letters within a row are significantly different (P<
a,bDifferent letters within a row are significantly different (P<
0.05)
0.05).
x,yDifferent letters within a column are significantly different
(P< 0.05)
1Standard errors of the mean among different fat sources
within the same irradiation dose.
2Standard errors of the mean among different irradiation
doses within the same fat sources.
1Standard errors of the mean among different fat sources
could not be separated by the method
used (Table 4).
After 8 d of storage in vacuum-packaging (Table 5), irradiated pork sausages
produced more 1-pentene+hexane, 1heptene, 2-propanone, 1-nonene, and total volatiles than nonirradiated. However,
pork sausages prepared with lard or corn
oil produced more hexanal and 1-heptanol when nonirradiated or irradiated at
low dose (2.5 kGy) than when irradiated at
high dose (4.5 kGy). Production of some
minor volatile compounds was inconsistent.
No significant changes in the amount
of
irradiation-sensitive-compounds,
1heptene and 1-nonene, were observed
during the 8 d of storage in vacuum packaging. Hexanal content in sausage prepared with lard or corn oil and vacuumpackaged showed a decreasing trend with
the increase of irradiation dose at Day 8,
but that of sausages prepared with flaxseed oil was not consistent (Tables 4 and
5). Shahidi and Pegg (1994) observed a
marked decrease in hexanal content upon
extended storage and suggested that the
reactions of hexanal with meat components or its further oxidation to hexanoic
acid were responsible for the reduction of
hexanal.
With aerobic packaging, all irradiated
sausages produced more 1-heptene, propanal, 2-propanone, and 1-nonene than
nonirradiated ones at Day 0. Irradiated
sausages prepared with lard or corn oil
produced more 1-pentene+hexane than
nonirradiated ones. Irradiation influenced
the content of pentanal, 2-methylpentanal, and sec-butanol in the sausages prepared with lard or corn oil but its effect was
not consistent. The amounts of 3-heptanol, 1-pentanol, and 1-heptanol generally showed decreasing trends as irradiation dose increased, but the changes were
not always significant (Table 6). Sausage
prepared with lard and irradiated at 4.5
kGy produced more total volatiles than
did nonirradiated or irradiated at 2.5 kGy.
After 8 d of storage in aerobic packaging,
all irradiated sausages produced more 1heptene, 1-nonene, and total volatiles
than nonirradiated ones (P < 0.05, Table
7). The amounts of 3-heptanol, 1-pentanol, 1-hexanol, and 1-heptanol showed
decreasing trends as irradiation dose increased, but the changes were not always
significant (Table 7).
Propanal, pentanal, and hexanal contents in sausages prepared with lard or
within the same irradiation dose.
2Standard errors of the mean among different irradiation
doses within the same fat sources.
Vol. 65, No. 2, 2000—JOURNAL OF FOOD SCIENCE
271
FoodChemistryandToxicology
Aerobic-packaged sausage irradiated at
4.5 kGy had higher 2-thiobarbituric acid
reactive substances (TBARS) than sausage nonirradiated or irradiated at 2.5 kGy
at Day 0 regardless of fat sources (Table
2). In vacuum-packaging, sausages irradiated at 4.5 kGy had higher TBARS than
those of nonirradiated or irradiated at 2.5
kGy in flaxseed oil treatment: however, the
difference generated by irradiation disappeared after 8 d of storage (Table 3).
TBARS of sausage prepared with lard
was higher than those with corn or flaxseed oil in both packaging methods during
storage. Sausage prepared with flaxseed
oil had a higher polyunsaturated fatty
acid content but produced a lower extent
of lipid oxidation than other treatments
probably because of high tocopherol content present in flaxseed oil. Lard and corn
oil used in this study were vitamin Estripped, but flaxseed oil was not because
we could not find stripped flaxseed oil.
High vitamin E content in muscle by dietary supplementation reduced cholesterol oxidation in chicken muscle (Galvin and
others 1998) and was helpful in maintaining low TBARS values in irradiated turkey
breast and leg meat patties during the 7-d
storage (Ahn and others 1997).
After 8 d of storage, aerobic-packaged
sausages prepared with flaxseed oil produced as high TBARS as with corn oil suggesting that high linolenic acid compensated antioxidant effect of vitamin E in
sausages prepared with flaxseed oil under
aerobic conditions. In an oxygen-free environment, however, the rate of lipid oxidation in sausages was influenced mostly
by the amount of tocopherol, and fatty
acid composition of the product had little
effect. During 8 d of storage, the TBARS of
aerobic-packaged sausages increased 2.2to 4.5-fold. However, TBARS of vacuumpackaged sausages did not increase.
Volatiles of Irradiated Sausage with Different Fatty Acid Composition . . .
corn oil increased significantly during 8-d
storage in aerobic conditions (Tables 6
and 7). Sausage made with flaxseed oil,
which contained high levels of n-3 fatty
acid (18:3) susceptible to oxidative
change, also showed similar increases in
propanal and hexanal content during the
8-d storage in aerobic conditions (Table 6
and 7). This indicates that high g-toco-
Table 4—Production of volatiles in vacuum-packaged, irradiated cooked pork sausage after 0-d storage at 4 ⬚C
Lard
Irradiation dose
Corn oil
FoodChemistryandToxicology
0 kGy
2.5 kGy
4.5 kGy
SEM
0 kGy
Volatiles
1-Pentene, hexane 169.7
1-Heptene
14.2c
Propanal
8.2
2-Propanone
22.3
1-Nonene
6.7c
Pentanal
21.3
2-Methylpentanal
124.1
2-Pentanone
14.9
Sec-butanol
83.3
Hexanal
73.0
3-Heptanol
2.7
1-Pentanol
13.5a
Cyclohexanone
1.9
1-Hexanol
1.9
Nonanal
2.5
1-Heptanol
4.8a
Total volatiles
564.8
162.9
42.4b
9.2
22.0
22.6b
25.1
111.9
13.6
72.7
62.7
2.2
11.3b
1.9
1.9
2.7
3.8ab
568.8
153.3
68.5a
7.7
23.8
34.5a
22.8
103.0
14.3
68.4
48.6
2.0
9.6b
1.9
1.9
2.9
3.2b
566.6
10.6
6.0
1.2
0.6
0.8
1.8
6.6
1.6
4.9
7.1
0.2
0.5
–
–
0.1
0.4
23.7
87.7
7.3c
5.6
15.4c
7.0c
13.6b
62.8
6.6b
43.4
42.2
2.2
10.8
1.9
1.9
2.7
3.5
314.2b
2.5 kGy
4.5 kGy
Area (ion count x 1000)
101.6
83.8
34.6b
62.6a
6.2
7.0
21.1b
26.2a
19.7b
33.6a
23.2a
22.9a
111.9
105.1
15.1a
13.5a
76.9
70.5
50.9
50.5
2.0
1.9
9.8
9.7
1.9
1.9
1.9
1.9
2.8
2.9
3.3
2.7
482.5a
496.4a
Flaxseed oil
SEM
0 kGy
2.5 kGy
4.5 kGy
6.6
3.5
0.4
0.4
0.5
2.1
13.5
1.7
9.3
6.4
0.1
0.6
–
0.1
0.4
31.8
30.3
6.6c
7.0b
19.0c
6.6c
17.4
89.5
10.9
64.6
23.9
4.9a
7.5
2.3
3.1
2.6a
1.9
297.9b
36.6
32.4b
10.0a
23.0b
20.0b
18.7
95.5
10.8
69.0
28.5
4.2b
7.6
2.2
3.4
2.2b
1.9
364.6b
38.2
61.5a
10.4a
26.4a
35.0a
17.5
87.4
11.4
63.5
23.4
3.8b
7.6
2.3
3.5
2.2b
1.9
395.9a
SEM
2.8
0.8
0.5
0.4
0.6
0.5
3.5
0.4
2.8
1.7
0.2
0.2
0.1
0.1
0.1
8.1
a-cDifferent letters within the same fat source are significantly different (P < 0.05); n = 12.
SEM: Standard errors of the mean among different irradiation within a fat source.
Table 5—Production of volatiles in vacuum-packaged, irradiated cooked pork sausages after 8-d storage at 4 ⬚C
Lard
Irradiation dose
Corn oil
0 kGy
2.5 kGy
4.5 kGy
SEM
0 kGy
Volatiles
1-Pentene, hexane 135.5b
1-Heptene
14.4c
Propanal
12.0b
2-Propanone
20.5b
1-Nonene
8.5c
Pentanal
13.1
2-Methylpentanal
72.8
2-Pentanone
11.4
Sec-butanol
46.2
Hexanal
71.0a
3-Heptanol
2.4a
1-Pentanol
14.1
Cyclohexanone
1.9
1-Hexanol
1.9
Nonanal
2.0
1-Heptanol
4.1a
Total volatiles
431.5b
157.7a
47.6b
12.9ab
25.3a
22.5b
9.3
72.8
10.8
46.2
57.5ab
2.1ab
14.0
1.9
1.9
1.9
3.4ab
487.9ab
165.9a
73.1a
13.8a
26.6a
34.2a
11.2
71.9
10.3
45.3
47.3b
2.0b
10.0
1.9
1.9
1.9
2.8b
520.2a
7.5
1.9
0.3
0.6
0.9
0.9
3.6
1.2
2.5
5.9
0.1
1.7
0.0
0.0
0.0
0.3
19.0
37.3c
9.1c
7.9
18.6c
6.7c
15.7
73.6
12.3
49.9
68.9a
2.0
13.0a
1.9
1.9
1.9b
3.3a
323.9b
2.5 kGy
4.5 kGy
Area (ion count x 1000)
52.8b
68.8a
39.7b
64.2a
9.6
8.6
23.1b
28.7a
19.2b
34.2a
13.4
17.1
84.6
73.6
14.6
12.4
57.2
49.9
62.4a
44.4b
2.0
2.2
11.5b
10.2c
1.9
2.0
1.9
2.0
2.0b
2.5a
3.0a
2.0b
398.8a
422.8a
Flaxseed oil
SEM
0 kGy
2.5 kGy
4.5 kGy
2.3
1.9
0.5
0.5
0.8
1.7
4.5
0.9
3.4
3.8
0.1
0.3
0.0
0.0
0.1
0.1
11.7
30.9c
9.3c
12.1b
20.8b
7.9c
14.2
67.9
9.8
47.7
29.0
2.6
8.9
2.4
3.0
2.5
2.0
271.0c
37.4b
33.0b
13.4a
22.9b
19.1b
14.9
71.7
11.0
50.0
28.2
2.5
8.2
2.1
3.2
2.0
2.0
321.4b
49.9a
58.9a
14.1a
27.0a
33.2a
13.5
62.8
8.8
44.7
29.0
2.5
8.3
2.2
3.4
2.0
2.0
362.1a
SEM
1.3
0.8
0.4
0.7
0.4
0.6
4.6
1.2
3.4
1.7
0.1
0.3
0.1
0.2
0.2
9.9
a-cDifferent letters within the same fat source are significantly different (P < 0.05); n = 12.
SEM: Standard errors of the mean among different irradiation within a fat source.
Table 6—Production of volatiles in aerobic-packaged, irradiated cooked pork sausages after 0-day storage at 4 ⬚C
Lard
Irradiation dose
0 kGy
Volatiles
1-Pentene, hexane 109.1b
1-Heptene
9.6c
Propanal
3.8c
2-Propanone
20.5b
1-Nonene
8.6c
Pentanal
15.9b
2-Methylpentanal
63.8b
2-Pentanone
8.1
Sec-butanol
51.6ab
Hexanal
75.4
3-Heptanol
2.2a
1-Pentanol
13.6a
Cyclohexanone
1.9
1-Hexanol
1.9
Nonanal
3.0
1-Heptanol
4.1a
Total Volatiles
392.8b
2.5 kGy
122.4ab
40.4b
4.3b
25.3a
23.5b
15.4b
49.7b
6.9
42.3b
67.8
1.9b
11.6b
1.9
1.9
2.8
3.5b
421.3b
4.5 kGy
139.7a
63.6a
6.6a
26.4a
33.2a
25.6a
106.0a
14.7
79.1a
62.6
1.9b
10.7b
1.9
1.9
2.5
2.9c
579.1a
Corn oil
SEM
5.6
1.0
0.5
0.7
0.8
2.4
13.0
2.2
9.0
6.0
0.1
0.5
0.2
0.2
32.6
0 kGy
98.7b
7.1c
5.4b
16.8c
5.2c
17.8ab
71.9ab
9.5
53.0ab
59.9
2.2
12.9a
1.9
1.9
2.0
3.8
370.0
2.5 kGy
Area (ion count x 1000)
120.7ab
127.9a
38.2b
74.7a
7.0a
7.6a
22.8b
26.0a
17.8b
34.0a
22.7a
15.9b
83.1a
50.3b
13.1
7.9
61.6a
37.5b
67.0
57.2
2.1
1.9
12.8a
10.4b
1.9
1.9
1.9
1.9
2.2
2.1
3.5
2.6
477.2
459.6
a-cDifferent superscript letters within the same fat source are significantly different (P < 0.05); n = 12.
SEM: Standard errors of the mean among different irradiation within a fat source.
272 JOURNAL OF FOOD SCIENCE—Vol. 65, No. 2, 2000
4.5 kGy
Flaxseed oil
SEM
0 kGy
2.5 kGy
4.5 kGy
7.3
5.2
0.4
0.4
0.5
1.4
7.5
2.1
5.5
6.2
0.1
0.5
0.1
0.3
28.1
25.7
7.7c
10.0b
19.7b
13.6c
25.6
125.4
16.3
90.9
42.0
5.8a
11.1
2.4a
3.3
2.5
1.9
402.8
31.6
36.7b
14.0a
23.7a
22.4b
20.8
92.2
11.8
67.4
38.7
5.2b
8.7
2.3a
3.4
2.6
1.9
383.2
54.4
76.8a
13.8a
24.8a
34.8a
23.2
105.1
13.8
75.8
41.4
4.1c
9.6
2.0b
3.3
2.5
1.9
487.0
SEM
9.1
6.1
0.5
0.4
1.6
1.9
11.4
1.4
8.2
3.4
0.2
0.7
0.1
0.1
0.1
33.3
Table 7—Production of volatiles in aerobic-packaged, irradiated cooked pork sausages after 8-d storage at 4 EC
Lard
0 kGy
2.5 kGy
4.5 kGy
Corn oil
SEM
0 kGy
4.5 kGy
Flaxseed oil
SEM
0 kGy
2.5 kGy
4.5 kGy
8.7
6.5
1.6
6.0
1.3
2.9
6.2
1.4
4.0
28.4
0.2
1.5
0.1
0.2
0.2
0.6
36.8
49.5b
22.7c
88.8
21.0c
10.6c
23.6
77.6
13.6
56.5
239.9
14.8a
30.0a
6.4
4.2
2.3
5.2
666.5c
52.1b
59.8b
82.9
25.6b
24.6b
21.2
93.6
12.4
62.2
263.3
13.3b
28.3ab
6.2
4.1
2.1
5.0
756.0b
67.5a
92.8a
87.3
29.8a
39.1a
25.9
94.3
14.3
64.1
266.2
12.4b
26.6b
6.0
4.1
2.5
4.6
837.2a
SEM
Area (ion count ∞ 1000)
Volatiles
1-Pentene, hexane 264.6
1-Heptene
16.7c
Propanal
25.8
2-Propanone
46.2
1-Nonene
21.3b
Pentanal
29.7b
2-Methylpentanal
135.1
2-Pentanone
14.3
Sec-butanol
89.4
Hexanal
275.5
3-Heptanol
5.4
1-Pentanol
48.0
Cyclohexanone
3.0
1-Hexanol
5.9a
Nonanal
3.4
1-Heptanol
9.2
Total Volatiles
993.3b
2.5 kGy
234.2
54.7b
40.1
54.1
23.3b
40.0a
140.5
14.9
92.9
302.6
5.0
39.5
3.4
3.0b
3.4
10.0
1061.4ab
275.8
87.1a
39.0
67.7
35.4a
43.3a
159.3
18.7
103.9
294.7
4.7
35.6
3.1
2.8b
3.5
9.1
1183.4a
15.7
8.3
3.7
8.2
3.3
2.2
17.5
1.8
11.2
16.7
0.3
3.4
0.3
0.5
0.2
0.3
43.4
80.9
15.3c
20.1b
44.5
8.9c
41.4ab
112.2
14.2
74.3
338.4
4.7a
45.3a
2.5b
3.5a
2.7
9.5a
818.5b
104.2
65.0b
28.3a
28.3
21.7b
49.2a
122.7
17.4
78.9
405.2
4.5a
43.8a
3.0a
2.6b
3.0
9.4a
986.0a
107.7
108.1a
29.1a
39.5
37.5a
36.3b
119.3
18.6
78.4
320.1
3.5b
34.5b
2.2b
2.2c
2.6
6.5b
945.6a
4.4
1.7
5.8
0.3
0.6
2.9
7.0
1.2
3.5
16.1
0.3
0.7
0.3
0.1
0.1
0.4
23.9
a-cDifferent superscript letters within the same fat source are significantly different (P < 0.05); n = 12.
SEM: Standard errors of the mean among different irradiation within a fat source.
pherol content (Table 1) in sausage with
flaxseed oil slowed a significant antioxidant effect but could not prevent oxidative change in cooked sausages under aerobic conditions. Ahn and others (1998b)
reported that dietary vitamin E supplementation was effective enough to control
lipid oxidation of raw meat but was not
sufficiently active for controlling oxidation
in cooked turkey meat during storage in
aerobic conditions. Katusin-Rasem and
others (1992) reported that irradiation-induced oxidation was dose-dependent and
the presence of oxygen had a significant
effect on the rate of oxidation. Hexanal, an
indicator of oxidative deterioration, was
not influenced by irradiation dose, indicating that the production of hexanal during storage was closely related to lipid oxidation but not to irradiation. Larick and
others (1992) found that meat from animals fed high-safflower diets produced
more pentanal, hexanal, 2-heptanone,
trans-2-heptanal, 2-pentylfuran, 2-ethyl1-hexanol, decanal, and undecanal than
did tallow. Larick and others (1992) also indicated that the amount of aldehydes
could be an indicator of the oxidative stability of the meat. Lopez-Bote and others
(1997) reported that meat from rabbits fed
a sunflower oil diet was more susceptible
to lipid oxidation than that meat from rabbits fed an olive oil diet, and diets rich in
C18:2 resulted in increased pentanal, hexanal, and total volatile aldehydes production in meat. The amounts of 1-heptene
and 1-nonene also increased significantly
during storage, indicating that these compounds can be produced not only by irradiation but also by oxidation of lipids.
The amounts of 1-heptene and 1-nonene increased 3- to 5-fold by irradiation regardless of fat source, packaging, and storage time. Singh and others (1993) report-
Table 8—Probability value (Pr > F) of storage and packaging effect on the production of
volatiles from sausage prepared with different fat sources
Storage1
Volatiles
1-Pentane, hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Sec-butanol
Hexanal
3-Heptanol
1-Pentanol
Cyclohexanone
1-Hexanol
Nonanal
1-Heptanol
Total volatiles
Lard
0.0001
0.25
0.0001
0.0001
0.38
0.22
0.16
0.31
0.52
0.0001
0.0001
0.0001
0.0001
0.0011
0.71
0.0001
0.0001
Packaging2
Corn oil Flaxseed oil
0.0001
0.16
0.0001
0.0003
0.60
0.0006
0.04
0.001
0.13
0.0001
0.0001
0.0001
0.0001
0.0001
0.95
0.0001
0.0001
0.004
0.25
0.0001
0.06
0.87
0.129
0.0001
0.20
0.0001
0.0001
0.0001
0.0001
0.0001
0.003
0.03
0.0001
0.0001
Lard
0.01
0.80
0.0003
0.0001
0.39
0.0002
0.15
0.77
0.02
0.0001
0.0001
0.0001
0.0001
0.001
0.0001
0.0001
0.0001
Corn oil Flaxseed oil
0.0001
0.10
0.0001
0.003
0.83
0.0001
0.31
0.39
0.23
0.0001
0.0001
0.0001
0.0001
0.0003
0.89
0.0001
0.0001
0.02
0.05
0.0001
0.33
0.22
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.08
0.0001
0.0001
1Irradiation and packaging treatments were pooled. n = 48.
2Irradiation and storage treatments were pooled. n = 48.
ed that formation of nonane could be
used as a marker of irradiation in homogenized bacon. However, nonane was not
detected by the method used. The
amounts of some volatile compounds decreased during the 8-d storage when the
irradiation dose and packaging treatments were pooled and analyzed (Table
8).
In general, the production of total volatiles was highest in sausage prepared with
lard and lowest in sausage prepared with
flaxseed oil except for the samples that
were aerobic-packaged at 0 d storage (Tables 4, 5, and 7). Sausage made with lard
contained a large proportion of saturated
fatty acids but showed the highest production of total volatiles. This indicated
that the presence of antioxidant (tocopherols) significantly influenced production of volatile compounds and off-flavor
generation. This indicated that the production of volatiles was more influenced
by the content of antioxidant than by fatty
acids in the product. No significant
change in volatile production in vacuumpackaged sausage during storage indicates that vacuum-packaging prevented
oxidation almost completely during the 8d storage. However, irradiation-sensitive
compounds (1-heptene and 1-nonene)
were not influenced by oxygen availability. If these hydrocarbon compounds were
responsible for irradiation odor, packaging
methods would not reduce off-flavor
problems of irradiated meat.
TBARS correlated well (r2 > 0.7, p < 0.01)
with propanal, hexanal, 3-heptanol, 1pentanol, cyclohexanone, 1-heptanol, and
total volatiles in all sausages with aerobic
packaging, indicating that these compounds are highly lipid oxidation-dependent (Table 9). In contrast, 1-heptene and
1-nonene showed very low correlation coefficients with TBARS in aerobic packaging, indicating that lipid oxidation-in-
Vol. 65, No. 2, 2000—JOURNAL OF FOOD SCIENCE
273
FoodChemistryandToxicology
Irradiation dose
Volatiles of Irradiated Sausage with Different Fatty Acid Composition . . .
duced and irradiation-induced volatile
compounds could be separated. Almost all
volatile compounds in vacuum-packaging
had no relationship with TBARS, and some
of them showed decreasing trends with
storage. This indicated that lipid oxidation
could not progress without oxygen even in
cooked meat products.
Conclusion
A
N OXYGEN - FREE ENVIRONMENT CAN
FoodChemistryandToxicology
minimize production of off-odor compounds from lipid oxidation. However,
vacuum packaging may not control the
production of irradiation-dependent volatiles in pork sausage. Irradiation odor may
be related to the combination of volatile
compounds produced by radiolysis and
lipid oxidation.
Materials and Methods
Sample preparation
Lean pork was purchased from a local meat packer and ground through a
9-mm plate twice. Pork sausages were
prepared with the lean meat, oil
(stripped lard, stripped corn oil, or unstripped flaxseed oil at 10% of weight of
lean meat), NaCl (2%), and ice water
(10%). The emulsified meat batters
were stuffed into collagen casings (3 cm
in diameter) and cooked in a smokehouse to an internal temperature of 72
EC. After cooling in ice water for 20 min,
sausages were sliced to 2-cm-thick pieces (approximately 30 g) and vacuumpackaged individually into oxygen-impermeable
nylon/polyethylene
bags
(9.3 mL O 2 /m 2 /24 hr at 0 EC; Koch, Kansas City, Mo., U.S.A.) to minimize oxidative changes between sample preparation and delay before irradiation. After
storing overnight in a 4 EC refrigerator,
half of the samples were left as vacuumpackaged and the other half were cut
open and flushed with air to produce
aerobic-packaged conditions before irradiation. Sausages were irradiated at 0,
2.5, or 4.5 kGy absorbed dose by using a
Linear Accelerator (Circe IIIR, Thomson
CSF, Linac, France). Irradiated samples
were stored in a 4 EC refrigerator for up
to 7 d.
Lipid oxidation, fat content, and
fatty acid composition
Lipid oxidation was determined using
a spectrophotometer (DU series 600,
Beckman Instruments Inc., Fullerton,
Calif., U.S.A.) as described (Ahn and others 1998b). TBA-reactive substances
(TBARS) values were expressed by mg
Table 9—Correlation coefficients between volatile compounds and TBARS of cooked pork
sausages prepared with different fat sources and packaging conditions
Lard
Volatiles
1-Pentane, hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Sec-butanol
Hexanal
3-Heptanol
1-Pentanol
Cyclohexanone
1-Hexanol
Nonanal
1-Heptanol
Total volatiles
Vacuum
0.05
-0.04
-0.17
-0.20
-0.07
0.32
0.07
0.02
0.04
0.35
0.24
0.07
-0.01
-0.01
0.41
0.33
0.13
Corn oil
Aerobic
0.88**
0.15
0.82**
0.46
0.15
0.57
0.43
0.31
0.48
0.89**
0.91**
0.91**
0.71*
0.71*
0.56
0.86**
0.80*
Vacuum
-0.04
-0.11
0.12
-0.00
-0.16
0.06
-0.04
-0.20
-0.12
0.39
0.22
0.49
0.02
0.02
-0.30
0.21
-0.13
Aerobic
-0.04
0.16
0.86**
0.20
0.04
0.84*
0.50
0.38
0.38
0.94**
0.93**
0.96**
0.74*
0.70*
0.60
0.90**
0.82**
Flaxseed oil
Vacuum
0.20
0.53
0.19
0.51
0.59
0.09
0.07
0.16
0.08
-0.17
-0.17
-0.23
-0.14
-0.13
-0.23
-0.09
0.47
Aerobic
0.51
0.13
0.89**
0.20
-0.14
0.19
-0.48
-0.24
-0.53
0.90**
0.88**
0.93**
0.79**
0.80*
-0.06
0.88**
0.79*
*Significant at P < 0.01; **Significant at P < 0.001.
malondialdehyde (MDA) per kg meat.
Total fat content was determined by the
Folch extraction method (Folch and others 1957). Fatty acid methylation was
performed with BF3 -methanol (14% solution, Supelco, Bellefonte, Pa., U.S.A.).
The fatty acid methyl esters were separated by a Hewlett Packard gas chromatograph (GC, Model 6890; Hewlett
Packard Co., Wilmington, Del., U.S.A.)
equipped with a flame ionization detector. A split inlet (split ratio, 29:1) was
used to inject samples into a HP-5 capillary column (0.25 mm H 30 m H 0.25 ␮m),
and ramped oven temperature was used
(80 EC for 0.3 min, increased to 180 EC at
30 EC/min, and increased to 230 EC at 6
EC/min). Inlet temperature was 180 EC
and detector 280 EC. Helium was the carrier gas at constant flow of 1.1 mL/min.
Detector air, H 2, and make-up gas (He)
flows were 300 mL/min, 30 mL/min, and
28 mL/min, respectively.
(40 mL/min) for 11 min. Volatiles were
trapped using a Tenax/silica/charcoal
column (Tekmar-Dohrmann, Cincinnati,
Ohio, U.S.A.), desorbed for 1 min at
220 EC. The temperature of transfer lines
was maintained at 155 EC. A split inlet
(split ratio, 49:1) was used to inject volatiles into an HP-wax bonded polyethyleneglycol column (60 m, 250 ␮m i.d., 0.25
␮m nominal), and ramped oven temperature was used (32 EC for 1 min, increased to 40 EC at 2 EC/min, to 50 EC at
5 EC/min, to 70 EC at 10 EC/min, to
140 EC at 20 EC/min, to 200 EC at 30 EC/
min and held for 5 min). Helium was the
carrier gas at constant flow of 1.1 mL/
min. The ionization potential of MS was
70 eV, scan range was 50 to 550 m/z, and
scan velocity was 2.94 scan/sec. The
identification of volatiles was achieved
by comparing mass spectral data with
those of the Wiley library (Hewlett Packard Co., Wilmington, Del., U.S.A.). The
peak area (total ion counts H 10 3) was reVolatile compound analysis
ported as the amount of volatiles rePrecept II and Purge-and-Trap con- leased.
centrator 3000 (Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.) were used to purge Vitamin E analysis
Sausage (2 g) was homogenized in 10
and trap added volatile compounds. A
GC (Model 6890, Hewlett Packard Co., mL (wt/vol) of phosphate-EDTA buffer
Wilmington, Del., U.S.A.) with a mass se- (pH 7.0). The amounts of a- and g-tocolective detector (MSD, Model 5973, pherol were determined using a high
liquid
chromatograph
Hewlett Packard Co.) was used to identi- performance
fy and quantify the volatile compounds. (HPLC; Shimadzu Co., Kyoto, Japan) as
The sample (2 g) was placed in a sam- described by Ahn et al. (1995).
ple vial (40 mL), capped tightly, and
placed on the sample holder maintained Statistical analysis
at refrigerated temperature (3 EC). OxyTwo-way analysis of variance (SAS Ingen absorber (Ageless, ZPT-50; Mitsub- stitute, Inc., 1989) was used to deterishi Gas Chemical America Inc., New mine the effect of irradiation dose and
York, N.Y., U.S.A.) was used to minimize different fat sources. The total number
oxidative changes during analysis. Sam- of samples used for the experiment was
ples were purged at 40 EC with helium 144 (3 irradiation doses H 3 fat sources H 2
274 JOURNAL OF FOOD SCIENCE—Vol. 65, No. 2, 2000
Reference
Ahn DU, Kawamoto C, Wolfe FH, Sim JS. 1995. Dietary
alpha-linolenic acid and mixed tocopherols, and packaging influence lipid stability in broiler chicken breast
and leg muscle tissue. J. Food Sci. 60:1013-1018.
Ahn DU, Olson DG, Lee JI, Jo C, Wu C, Chen X. 1998a.
Packaging and irradiation effects on lipid oxidation
and volatiles in pork patties. J. Food Sci. 63:15-19.
Ahn DU, Sell JL, Jeffery M, Jo C, Chen X, Wu C, Lee JI.
1997. Dietary vitamin E affects lipid oxidation and
total volatiles of irradiated raw turkey meat. J. Food
Sci. 62: 954-959.
Ahn DU, Sell JL, Jo C, Chen X, Wu C, Lee, JI. 1998b. Effects of dietary vitamin E supplementation on lipid
oxidation and volatiles content of irradiated cooked
turkey meat patties with different packaging. Poultry
Sci. 77:912-920.
Ajuyah AO, Ahn DU, Hardin RT, Sim JS. 1993. Dietary
antioxidants and storage affect chemical characteristics of w-3 fatty acid enriched broiler chicken meats. J.
Food Sci. 58:43-46.
Buckley D L, Morrissey PA, Gray JI. 1995. Influence of
dietary vitamin E on the oxidative stability and quality of pig meat. J. Anim. Sci. 71:3122-3130.
Folch J, Less M, Sloane-Stanley GM. 1957. A simple
method for the isolation and purificatio of total lipids
form animal tissues. J. Biol. Chem. 226:497-505.
Frankel EN. 1991. Recent advance in lipid oxidation: A
review. J. Sci. Food Agric. 54:495-511.
Galvin K, Morrissey PA, Buckley DJ. 1998. Cholesterol
oxides in processed chicken muscle as influenced by
dietary ␣-tocopherol supplementation. Meat Sci. 48:
1-9.
Gants R. 1998. Irradiation: Weighing the risks and benefits. Meat Poultry, April: 34-42.
Hashim IB, Resurreccion AVA, McWatters KH. 1995. Disruptive sensory analysis of irradiated frozen or refrigerated chicken. J. Food Sci. 60: 664-666.
Hau LB, Liew MH, Yeh LT. 1992. Preservation of grass
used to compare differences among
mean values of TBARS values and the
amount of volatile production. Mean values and standard errors of the mean
prawns by ionizing irradiation. J. Food Protect. 55:
198-202.
Kanatt SR, Paul P, D’Souza SF, Thomas P. 1998. Lipid
peroxidation in chicken meat during chilled storage as
affected by antioxidants combined with low-dose gamma irradiation. J. Food Sci. 63: 198-200.
Katusin-Rasem B, Mihaljevic B, Razem D. 1992. Timedependent postirradiation oxidative chemical changes in dehydrated egg products. J. Agric. Food Chem.
40: 1948-1952.
Lakritz L, Fox JB Jr., Hampson J, Richardson R, Kohout
K, Thayer DW. 1995. Effect of gamma radiation on levels of a-tocopherol in red meats and turkeys. Meat Sci.
41:261-271.
Larick DK, Turner BE, Schoenherr WD, Coffey MT, Pilkington DH. 1992. Volatile compound content and fatty
acid composition of pork as influenced by linoleic acid
content of the diet. J. Anim. Sci. 70: 1397-1403.
Lee M, Sebranek J, Parrish FC Jr. 1996. Accelerated postmortem aging of beef utilizing electron-beam irradiation and modified atmosphere packaging. J. Food Sci.
61: 133-136, 141.
Liu HR, White PJ. 1992. Oxidative stability of soybean
oils with altered fatty acid compositions. J. Am. Oil
Chem. Soc. 69: 528-532.
Liu Q, Lanari MC, Schaefer DM. 1995. A review of dietary
vitamin E supplementation for improvement of beef
quality. J. Anim. Sci. 73:3131-3140.
Lopez-Bote C, Rey A, Ruiz J, Isabel B, Sanz-Arias R. 1997.
Effect of feeding diets high in monounsaturated fatty
acids and alpha-tocopheryl acetate to rabbits on resulting carcass fatty acid profile and lipid oxidation.
J. Anim. Sci. 64: 177-186.
Miller LA, White PJ. 1988. Quantification of carbonyl
compounds in oxidized low-linolenate, high-stearate
and common soybean oils. J. Am. Oil Chem. Soc. 65:
1328-1333.
Murano PS. 1995. Quality of irradiated foods. In: Murano EA, editor. Food Irradiation: A Sourcebook. Ames,
Ia.: Iowa State Univ. Press. p 63-87
(SEM) were reported. The relationships
between volatile compounds and TBARS
were analyzed by the SAS program and
correlation coefficients were provided.
Patterson RLS, Stevenson MH. 1994. Irradiation-induced
off-odor in chicken and its possible control. Br. Poultry Sci. 36: 425-441.
SAS Institute, Inc., 1989. SAS User’s guide®. Cary, N.C.:
SAS Institute Inc. 638 p.
Shahidi F, Pegg RB. 1994. Hexanal as an indicator of the
flavor deterioration of meat and meat products. Am.
Chem. Soc. Symp. Series 558: 256-279.
Shin TS, Godber JS. 1996. Changes of endogenous antioxidants and fatty acid composition in irradiated rice
bran during storage. J. Agric. Food Chem. 44: 567-573.
Singh H, Guerrero A, Kremers W. 1993. Nonane as a radiolytic product in irradiated bacon. J. Food Sci. 58: 4950.
Thayer DW, Fox JB Jr., Lakritz L. 1993. Effects of ionizing radiation treatments on the microbiological, nutritional, and structural quality of meats. In: ACS Symposium Series 528. Washington, D.C.: American Chemical Society. p 293.
Winne AD, Dirinck P. 1996. Studies on vitamin E and
meat quality. 2. Effect of feeding high vitamin E levels
on chicken meat quality. J. Sci. Food Agric. 44:16911696.
Woods RJ, Pikaev AK. 1994. Interaction of radiation with
matter. In: Applied Radiation Chemistry: Radiation
Processing. New York: John Wiley & Sons. p. 59-89
MS 19990629 received 6/21/99; revised 10/14/99; accepted 12/3/99.
Journal Paper No. J - 18249 of the Iowa Agriculture and Home
Economics Experiment Station, Ames, IA 50011. Project No.
3322, supported by Hatch Act and the Food Safety Consortium.
Authors are with the Department of Animal Science, Iowa State University, Ames, IA 50011-3150.
Direct inquiries to author Ahn (E-mail:
duahn@iastate.edu).
Vol. 65, No. 2, 2000—JOURNAL OF FOOD SCIENCE
275
FoodChemistryandToxicology
packaging methods H 2 storage H 4 replications), and the determined significance level was p < 0.05. The StudentNewman-Keul’s multiple range test was